Comparative View of a Star Before and After the Installation of the Corrective Optics Space Telescope Axial Replacement (COSTAR)

January 13, 1994: This pair of images of a single star, taken with the European Space Agency's
Faint Object Camera (FOC), demonstrate that NASA's Hubble Space
Telescope has been restored fully to its planned optical performance.

The COSTAR mirrors remove the effect of spherical aberration in the HST's
primary mirror. The FOC will now be able to observe extremely faint
celestial objects with a clarity and sensitivity unmatched by ground-based
telescopes.